Boehringer's Pink Pill: It Ain't Viagra

A panel of U.S. Food and Drug Administration experts decided Friday that Boehringer Ingelheim's so-called "female viagra" drug, flibanserin, doesn't provide enough benefit to outweigh the risks. The panel voted 10-1 that the drug isn't effective and found the side effects unacceptable in an 11-0 vote. The FDA doesn't have to follow the panel's advice, although it usually does.

The drug failed to significantly increase sexual desire in premenopausal women with hypoactive sexual desire disorder, or low sex drive, in two Boehringer studies, according to an online FDA review posted Wednesday. Women taking the drug reported slightly more sexually satisfying experiences, but the FDA says in its review that an effective treatment would be "an overall increase in sexual desire regardless of whether a sexual event occurred or not."

Moreover, the FDA questioned the safety of the drug, as it noted increased side effects like depression, fainting and dizziness among women taking the pill. In the studies, 15% of women stopping taking flibanserin, compared to only 6.8% in the placebo group.

Satisfying Women: A $2 Billion Market

It's clear that flibanserin, designed to boost sex drive in women, is no Viagra. Since the launch of Pfizer's (PFE) little blue pill in 1998, which met with multibillion-dollar success, many pharmaceuticals and studies have aimed to fix "female sexual dysfunction."

And no wonder: It's a market some analysts project at $2 billion, estimating that more than 40% of women suffer from some form of sexual dysfunction. (Others are skeptical of the 40% estimate, saying a lack of established standards for normal sexual performance in women makes it difficult to define a disorder.)

But trials for female libido enhancers have mostly failed, in spite of the many different pharmaceutical approaches that have evolved over time. From drugs that increase blood flow to the genitals, like Viagra, companies have tried drugs that boost hormones and now those, like flibanserin, that change brain chemistry.

Flibanserin is related to the antidepressant family and affects serotonin levels and several other brain chemicals. Boehringer admits it's not sure how that boosts sex drive.

Solving the Mystery of Female Sexuality

Why has it proven so much harder to stimulate women than men? Arousal in women is far more complicated, many experts say, with a wider range of factors potentially playing a role in sex drive. It also may be more difficult to measure the effects of libido-enhancing drugs on women. Some experts are skeptical about the idea using the number of "sexually satisfying events," for example, as a measurement.